High-voltage temperature switch

ABSTRACT

A high-voltage temperature switch for a direct current circuit including a body formed of insulating material and defining an arc chute within which a fusible conductor or link is positioned, wherein the link establishes a circuit and opens upon being subjected to a given temperature to interrupt the circuit, and means for generating a magnetic field across the arc chute about the fusible link to blow out the arc in the event the link opens.

United States Patent Chester 11. Fluder Wheeling;

Carl Krisco, Oak Park, both of III. 9,633

Feb. 9, 1970 Oct. 12, 1971 Vapor Corporation Chicago, Ill.

Inventors Appl. No. Filed Patented Assignee HIGH-VOLTAGE TEMPERATURE SWITCH 5 Claims, 7 Drawing Figs.

US. Cl 337/282, 200/147 A, 337/165 Int. Cl H0lh 9/44, HOlh 85/38, HOlh 85/44 Field of Search 337/ 165, 166,185,273, 282, 290; 200/147 A 56] References Cited UNITED STATES PATENTS 3,090,854 5/1963 Kretzschmar ZOO/147 A 2,727,110 12/1955 Von HO0rn.... 337/165 2,185,039 12/1939 Smith 337/282 X 2,167,499 7/1939 Dickenson 337/282 X Primary Examiner-Bernard A. Gilheany Assistant ExaminerDewitt M. Morgan Attorneys-Julian Falk, Chester A. Williams, J r., Marshall J.

Breen and Kinzer, Dom and Zickert ABSTRACT: A high-voltage temperature switch for a direct current circuit including a body formed of insulating material and defining an arc chute within which a fusible conductor or link is positioned, wherein the link establishes a circuit and opens upon being subjected to a given temperature to interrupt the circuit, and means for generating a magnetic field across the arc chute about the fusible link to blow out the arc in the event the link opens.

PAIENTEDucI 12 l97| SHEETl 0F 2 INVENTORS CHESTER H. LUDER CARL 7 R1660 B 9.6 1

ATTORNEY PATENTEUUCT l2|97l 3,613,040

SHEET 20F 2 FIG] Y TNVENTORS CHESTER H. FLUDER {CARL ATTORNEY This invention relates in general to a circuit breaker or a switch responsive to a high-temperature condition to interrupt a circuit and correct the high-temperature condition, and more particularly to a high-voltage temperature switch to prevent overheat or fire hazards arising from certain fault conditions, for example such conditions that may be present on rapid transit cars.

Recent models of rapid transit cars have incorporated evaporators for air conditioning and heaters for heating the compartments as a single package in overhead installations. These heaters produce such a watts density that in the absence of airflow thereover, considerable damage to equipment and the cars and possibly fire can result. The lack of sufficientairflow, when the heaters are energized could be caused by a number of factors, such as broken blower belts, faulty blower motors, badly clogged filters, or welded contacts on the heater contactor control. It then becomes a problemto sense the overheat condition and prevent its escalation to the point of damage by interrupting the power source to the heater. Heretofore, there have been a number of devices commercia lly available and capable of sensing undesirable high temperature and capableof then interrupting light or moderate power sources. These devices are generally referred to as fusible links or heat limiters. However, these devices are not capable of interrupting high-voltage direct current circuits in the range of 600 to 750 volts as employed in rapid transit cars.

The present invention relates to a high-voltage temperature switch responding to an overheat condition to interrupt a high-voltage direct current circuit, and is thereby usefulto prevent overheat and fire hazards arising fror'trcertain fault conditions on rapid transit cars. The switch includes a molded body of insulating material including an elongated bar portion and upstanding walls from the bar portion coacting therewith to define an arc chute. Positive and negative terminals or busses are mounted on the bar in spaced relation. A fusible link connects between terminals to define a circuit therebetween, and which opens in response to being subjected to a predetermined high temperature. The fusible link includes an elongated member of insulated material arched in the center with terminal means at each end. A leaf spring conductor is permanently fastened to terminal means on one end of the insulating member and releasably fastened on the other end of the member to the other terminal means by a fusible metal. The leaf spring is bent over the arch portion of the member, and upon being released will spring up to separate the releasable end from the corresponding terminal means. The fusible metal softens upon being subjected to a given'temperature to allow release of the one end of the spring leaf. In order to blow out the arch between the releasable end of the spring leaf and the corresponding terminal means, a magnetic field is generated in the arc chute and about the fusible link. Generation of the magnetic field is by a pair of permanent magnets mounted on opposite sides of the arc chute in magnet cavities formed in the switch body.

It is therefore an object of this invention to provide a new and improved high-voltage temperature switch capable of interrupting high-voltage direct current circuits.

Another object of this invention is in the provision of a highvoltage temperature switch for use on rapid transit cars employing high-voltage direct current circuits to prevent overheat or fire conditions arising from certain fault conditions, and which responds to a predetermined high temperature to interrupt the circuit. i

A further object of this invention is in the provision of a high-voltage temperature switch for direct current circuits employing a fusible link encased in an insulating material defining an arc chute, and wherein a magnetic field is generated in the chute to achieve an adequate interrupting capability.

Other objects, features and advantages of the invention will be apparent from the following detailed disclosure, taken in conjunction with the accompanying sheets of drawings, wherein like reference numerals refer to like parts, in which:

' from the switch heater within safe limits. Such FIG. I is a perspective view of the high-voltage temperature switch of the invention;

FIG. 2 is a top plan view of the switch shown inFlG. 1;

FIG. 3 is an end elevational view taken along line 3-3 'of FIG. 2;

FIG. 4 is a perspective view of the fusible link as removed body; FIG. 5 is a side elevational view of the switch of FIG. 1;

FIG. 6 is a greatly enlarged fragmentary view, partly in section as taken through the center'of the switch on the longitudinal axis and illustrating the fusible link in operative or circuit establishing position; and

FIG. 7 is a view similar to FIG..6, but illustrating the fusible link in circuit-interrupting position.

The high-voltage temperature switch of the invention is especially useful for interrupting high-voltage direct current circuits in response tooverheat conditions, although it could also be used wherever there is a need in the electrical circuitry to interrupt a circuit pursuant to a high-heat condition. The switch is especially useful in rapid transit cars to protect against damage that might be caused by an electrically powered heater upon the failure of airflow thereover, where the airflow is necessary to maintain the heat condition at the heaters are powered by high voltage direct current circuits, such as 600 volts or higher, and difficulties are encountered in the interruption of such circuits with commercially available circuit-breaking devices. The present invention utilizes a heat-sensitive fusible link of a type well know in an-environment permitting interruption capability of high voltage direct current circuits, wherein an arc chute -is provided in coaction with a magnetic field'to blow out the v are created during opening of'the fusible link.

Referring now to the drawings, and particularly to FIGS. 1 to}; the high-voltage temperature switch of the invention, generally indicated by the numeral 10, includes a body 11 of insulating material formed to define an arc chute 12, a positive terminal or buss 13, a negative terminal or bus 14, a fusible link or conductor 15, and'magnetic means 16 for generating a magnetic field across the arc chute and about the fusible link 15.

The switching body 11 may be molded or otherwise formed of a suitable electrical insulating material capable of withstanding temperatures encountered when used in an area to detect a high-temperature condition. For example, the switch would be placed adjacent a heater in a rapid transit car so that it would sense an overheat condition of the heater and interrupt the circuit of the heater to prevent damage to it and surrounding structures. The body includes a bar portion 17 having an upper flat-surface I8, and upstanding walls 19 which coact with the flat surface or bottom wall 18 to define the arc chute 12. 'The upstanding walls extend from the opposite edges of the bottom wall 18 and are substantially parallel to each other, and in alignment with each other. However, it should be appreciated that the walls 19 need not be parallel to each other, as long asthey coact with the bottom wall 18 to define an arc chute .within which the fusible link 15 may be positioned.

The positive terminal 13 is mounted at one end of the flat surface 18, while the negative terminal 14 is mounted at the other end, and these terminals are of a suitable electrical conducting material such as copper. The positive terminal 13 is rectangular in shape and fastened to the switch body by a suitable capscrew 20. The negative terminal 14 is fastened to the surface 18 of the switch body by a capscrew 21. Further, the negative tenni'nal, while being generally rectangular in shape includes a necked down portion 22 which extends into the arc chute. Both the positive and negative tenninals facilitate the connection of the switch into a circuit, as well as connection to the fusible link 15.

The fusible link 15 which completes the circuit between the positive terminal 14 includes an elongated member 23 of suitable insulating material such as ceramic or steatite, and

forms a support for a positive terminal 24, a negative terminal terminals are of a suitable electrically conductive metal, such as copper, and differently shaped to facilitate the proper directional mounting of the fusible link on the switch body, As illustrated, the positive terminal has a rectangularly shaped end, while the negative terminal has a cylindrically shaped end. Both terminals are provided with suitable apertures through which fasteners may extend, and the apertures are spaced so that they align with like apertures in the positive and negative terminals 13 and 14 of the switch so that fasteners 27 and 28 may be utilized for securing the fusible link to the switch body and also for electrically connecting the fusible link to the positive and negative terminals of the switch. As seen in FIGS. 6 and 7, metal inserts 29 and 30 are molded in the body 11 of the switch for receiving the capscrews 27 and 28. Similarly, it will be appreciated that inserts are provided for the capscrews 20 and 21.

The positive and negative terminals 24 and 25 are respectively attached to metal rivets 31 and 32 which extend vertically through, the opposite ends of the fusible link elongated member 23. Solder or other suitable means may be employed for connecting the terminals to the rivets, and the rivets define a conductive path to the upper side of the member 23.

The leaf spring member 26 is permanently fastened to the rivet 31 at one end, such as by a suitable solder joint 33, and

, releasably attached at the other end to the rivet 32 by a heat fusible joint 34. The leaf spring member 26 may be formed of a suitable metal capable of providing good electrical conducion as well as facilitating the opening of the fusible link upon 3 I melting of the heat fusible joint 34. As illustrated, the leaf spring member includes an upper copper strip 35 and a lower spring steel strip 36, wherein the copper strip serves to conduct the electricity across the link, while the spring steel strip serves to open the link when the link is subjected to a given heat. It may be noted that the center portion of the elongated member-23 is arched upwardly to further facilitate the action of the leaf spring member 26 when the heat fusible joint 34 melts, and the releasable end of the spring member moves upwardly to a position like that shown in FIG. 7.

The heat-fusible joint 34 is defined by a fusible alloy that is softened upon being subjected to a predetermined heat condition. For example, the melting point of the alloy may define an opening temperature of l90to 450F. Therefore, it can be app'reciated that current passes through the leaf spring member 26, and when the fusiblejlink is subjected to a given temperature at which theheat-fusible joint will melt, the fusible alloy is softened and the releasable end of the spring member pops up I to open the circuit established between the positive and negative terminals of the switch.

Inasmuch as the opening of the fusible link when used in a high-voltage direct current circuit will cause a considerable arc, it is necessary to protect surrounding components by having the fusible link positioned in the arc chute 12. Further, since it would not be possible to eliminate the arcing between the releasable end-of the leaf spring member 26 and the upper end of the rivet 32, a magnetic field is generated across the are chute and in the area of the space between the releasable end of the spring member and the rivet 32 to blow out the arc. Effectively, the magnetic field elongates the arc in the blowing out process. The magnetic means 16 includes a pair of permanent magnets 40, one arranged on each side of the arc chute 12 to facilitate mounting of the permanent magnets 40 on the body 11 of the switch. Blow out magnetic cavities 41 are defined to receive the permanent magnets 40, which magnets may be cemented therein by a suitable adhesive.

The releasable end of the fusible link is at the negative side of the circuit established thereby, wherein the open area defined between the releasable end of the spring member 26 and the rivet 32 when the fusible link is open is well within the stronger portion of the magnetic field generated by the permanent magnets 40. This is especially evident by looking at FIG. 5, and it can further be appreciated that the permanent magnets are rectangular in shape and have a long axis that substantially parallels a line extending from the intersection of the spring member 26 and the elongated member 23 through the center of the open area defined between the, releasable end of the spring member 26 and the rivet 32 when thespring member is a popped-up position. Accordingly, the permanent magnets 40 on opposite sides of the arc chute are aligned with each other and arranged along a path inclined relative to the longitudinal axis of the switch bar member 17.

The polarity direction of the magnets 40 traverses the are chute, and in this respect the North Pole and the "South Pole are respectively designated as 400 and 40b From the foregoing, the operation of the switch of the invention can readily be appreciated, wherein during normal operation, the switch will provide a closed circuit between the positive and negative terminals 13 and I4, and when the switch is subjected to an overheat condition that might endanger the surrounding components, the fusible alloy joint 34 will melt and release the leaf spring member 26 to pop to the open position as shown in FIG. 7. Arcing across the releasable end of the spring member and the rivet 32 is then blown out by the magnetic field generated by the permanent magnets 40 to complete the interruption of the circuit. It can be appreciated that thereafter upon alleviating the fault condition causing the overheat, a new fusible link may be easily installed to thereafter again establish the circuit between positive and negative terminals of the switch.

It will be understood that modifications and variations may be effected without departing from the scope of the novel concepts of the present invention.

This invention is hereby claimed as follows:

1. A high-voltage temperature switch for a direct current cuit upon being subjected to a given temperature, means adjacent said chute continually creating a magnetic field therein and about said fusible conductor to blow out the are caused by opening of the fusible conductor, said fusible conductor including an elongated insulating member arched in the center, terminal means at opposite ends, a leaf spring means permanently attached to one of said terminal means and bent down over the arched center and releasably attached to the other terminal means by a heat-fusible metal that melts to release the one end of the leaf spring means in response to a given temperature and the area between the releasable end of the leaf spring means in released position and the corresponding terminal means being directly in the path of the magnetic field.

2. A high-voltage temperature switch as defined in claim 1, wherein the polarity direction of the magnetic field is compatible with the current direction through the fusible conductor.

3. A high-voltage temperature switch as defined in claim 1, wherein the polarity direction of the magnetic field traverses the fusible conductor.

4. A high-voltage temperature switch for a direct current circuit operable to interrupt the circuit upon being subjected to a given temperature, said switch comprising a body of insulating material, said body having an elongated bar and a pair of upstanding substantially parallel and aligned walls intermediate the ends of the bar and defining therewith an arc bar, a heat-fusible link connected between said tenninals to define a circuit and positioned on said bar within said are chute, means generating a magnetic field in said are chute about said fusible link to blow out the are caused by opening of the fusible link, said body including wall means coacting with said upstanding walls to define blow out magnet cavities I field traversing said are chute, said fusible link including an elongated insulating member arched in the center, terminal means at opposite ends, a leaf spring means permanently attached to one of said terminal means and bent down over the arched center and releasably attached to the other terminal means by a heat-fusible metal that melts to release the one end of the leaf spring means in response to a given temperature, and the area between the releasable end of the leaf spring means in released position and the corresponding terminal 1 a line extending 

1. A high-voltage temperature switch for a direct current circuit operable to interrupt the circuit upon being subjected to a given temperature, said switch comprising a body formed of insulating material in a shape to define an elongAted arc chute, positive and negative terminals, a heat-fusible conductor extending between said terminals and positioned in said arc chute, said fusible conductor normally completing a circuit between said terminals and opening to interrupt said circuit upon being subjected to a given temperature, means adjacent said chute continually creating a magnetic field therein and about said fusible conductor to blow out the arc caused by opening of the fusible conductor, said fusible conductor including an elongated insulating member arched in the center, terminal means at opposite ends, a leaf spring means permanently attached to one of said terminal means and bent down over the arched center and releasably attached to the other terminal means by a heat-fusible metal that melts to release the one end of the leaf spring means in response to a given temperature and the area between the releasable end of the leaf spring means in released position and the corresponding terminal means being directly in the path of the magnetic field.
 2. A high-voltage temperature switch as defined in claim 1, wherein the polarity direction of the magnetic field is compatible with the current direction through the fusible conductor.
 3. A high-voltage temperature switch as defined in claim 1, wherein the polarity direction of the magnetic field traverses the fusible conductor.
 4. A high-voltage temperature switch for a direct current circuit operable to interrupt the circuit upon being subjected to a given temperature, said switch comprising a body of insulating material, said body having an elongated bar and a pair of upstanding substantially parallel and aligned walls intermediate the ends of the bar and defining therewith an arc chute, spaced positive and negative terminals mounted on said bar, a heat-fusible link connected between said terminals to define a circuit and positioned on said bar within said arc chute, means generating a magnetic field in said arc chute about said fusible link to blow out the arc caused by opening of the fusible link, said body including wall means coacting with said upstanding walls to define blow out magnet cavities one on each side of said arc chute, said magnetic field generating means including a pair of permanent blow out magnets one in each blow out magnet cavity and arranged to produce a field traversing said arc chute, said fusible link including an elongated insulating member arched in the center, terminal means at opposite ends, a leaf spring means permanently attached to one of said terminal means and bent down over the arched center and releasably attached to the other terminal means by a heat-fusible metal that melts to release the one end of the leaf spring means in response to a given temperature, and the area between the releasable end of the leaf spring means in released position and the corresponding terminal means being directly in the path of the magnetic field.
 5. A high-voltage temperature switch as defined in claim 4 wherein said permanent magnets are rectangular in shape with a longitudinal axis substantially aligned with a line extending longitudinally of the fusible link and through the center of the opening created between the releasable end of the leaf spring means in released position and the corresponding terminal means. 